Aqueous aromatic polyurethane elastomeric articles and method of fabricating the same

ABSTRACT

An aqueous aromatic polyurethane elastomeric article is fabricated by an aqueous aromatic polyurethane dispersion, prepared by polyurethane prepolymers comprising wholly aromatic diisocyanates, especially toluene diisocyanate (TDI). And, a method of fabricating the elastomeric article is provided.

BACKGROUND

The present invention relates to an elastomeric article, and morespecifically to an aqueous aromatic polyurethane elastomeric article anda method of fabricating the same.

Natural rubber latex gloves are popular for use as safety gloves. Suchnatural rubber latex gloves, however, may cause allergies or contactdermatitis due to their composition, such as proteins allergens, andchemical substances added during the glove fabrication. To avoid thesedangers, some methods have been provided, for example, reduction ofnatural latex quantities or replacement with hypo-allergenic polymers.Nevertheless, elastomeric articles are often uncomfortable and not easyto wear. Powdered or halogenated gloves are proved to increase lubricityof the surface of gloves and more convenience to wear. Nevertheless, thepowder on surgical gloves may contaminate sterile areas and causefurther complications for the patient. For use in a precise equipment inthe electrical/electronic industry, powder may be a serious contaminant.Additionally, halogenated gloves may deteriorate quickly, resulting inembrittlement or color fading.

Current aqueous polyurethane (PU) gloves can provide more comfortabledonnability and avoid powder problems. Those aqueous polyurethanes aremade from aliphatic or cycloaliphatic diisocyantes, such as isophoronediisocyanate (IPDI), hexamethylene diisocyanate (HDI), and4,4′-dicyclohexylmethane diisocyanate (HMDI), will give betterhydrolytic resistance. Such diisocyantes, however, are expensive,increasing production cost. Additionally, conventional aqueouspolyurethane may crack during drying due to poor fusion between PUparticles after dipping or coating, resulting in deterioration oforiginal characteristics. Thus, an aqueous polyurethane elastomericarticle with low cost and optimal mechanical characteristics is requiredto be suitable for preparation in dipping or coating.

SUMMARY

The invention provides aqueous aromatic polyurethane elastomericarticles fabricated by an aqueous aromatic polyurethane dispersion,prepared by polyurethane prepolymers comprising wholly aromaticdiisocyanates, especially toluene diisocyanate (TDI).

The invention also provides a method of fabricating aqueous aromaticpolyurethane elastomeric articles, comprising the following steps. Anaqueous aromatic polyurethane solution is provided. A mold is thendipped in the solution. After the mold is lift out of the solution, anaqueous aromatic polyurethane film is formed on the mold surface. Thefilm is then dried and cooled. After the film is stripped, an aqueousaromatic polyurethane elastomeric article is formed.

A detailed description is given in the following embodiments.

DETAILED DESCRIPTION

The invention provides aqueous aromatic polyurethane elastomericarticles fabricated by an aqueous aromatic polyurethane dispersion,prepared by polyurethane prepolymers comprising wholly aromaticdiisocyanates, especially toluene diisocyanate (TDI).

The aromatic diisocyanate comprises at least one aromatic ring, such asphenyl and diphenyl. Substituted groups of the aromatic ring maycomprise halogen atoms, nitro, cyano, alkyl, alkoxy, alkyl halide,hydroxyl, carboxyl, amide, or amino.

The aromatic diisocyanate has formula (I) or (II):

wherein R₁ may comprise hydrogen atom or C1-6 alkyl, R₂ and R₃ may bethe same or different, such as hydrogen atom, C1-6 alkyl, C1-6 alkoxy,or C6 aryl, and n may be 0˜3.

The aromatic diisocyanate may comprise toluene diisocyanate (TDI),p-phenylene diisocyanate (PPDI), 4,4′-diphenylmethane diisocyanate(MDI), or p,p′-bisphenyl diisocyanate (BPDI).

The aqueous aromatic polyurethane dispersion is prepared by an aromaticdiisocyanate, at least one polyol, a low-molecular weight compound withat least two functional groups capable of reacting with isocyanategroups, and a hydrophilic compound containing active hydrogen. Thelow-molecular weight compound has a molecular weight of 60˜300.

In a method of fabricating an aqueous aromatic polyurethane elastomericarticle, aqueous aromatic polyurethane solution is provided, and a moldis dipped in the solution. The mold may be ceramic, metal, plastic, orrubber. After the mold is lift out of the solution, an aqueous aromaticpolyurethane film is formed on the mold surface. The film is then driedand cooled. After the film is stripped, an aqueous aromatic polyurethaneelastomeric article is formed.

According to practical requirements, the aqueous aromatic polyurethanesolution may comprise surfactant, thickener, humectant, stabilizingreagent, deforming agent, cross-linking agent, leveling agent, orplasticizer. The aqueous aromatic polyurethane solution is prepared asfollows. An aromatic diisocyanate, polyols, a diol containinghydrophilic groups, and solvents are mixed to form a solution comprisingaromatic polyurethane prepolymers. The solvent is an organic solventhaving a boiling point of 50˜2000°C. Next, the prepolymers are dispersedin an aqueous phase of the solution and extended by a chain-extendingcompound such as diamine or diol. After the solvent content is reducedby low-vacuum distillation or steam distillation if necessary, theaqueous aromatic polyurethane solution with organic solvent less than15% and solid contents of 10˜65 wt % is prepared.

The low-cost and high-performance elastomeric article of the inventionis prepared by aqueous aromatic polyurethane, without additionalmodifiers or additives. Mechanical properties of the elastomeric articlemay be similar to rubber or superior thereto, that is, originalcharacteristics of aqueous aromatic polyurethane are maintained duringdipping or coating.

The elastomeric article has an elongation of 150˜1000%, preferablyexceeding 650%, a tensile strength of 30˜850 kg/cm², preferablyexceeding 170 kg/cm² ,a 500% modulus of 10˜150 kg/cm², preferably lessthan 70 kg/cm², and a thickness of 0.05 ˜0.35 mm. The elastomericarticle may comprise glove, condom, or catheter.

According to product quality tests, an aqueous aromatic polyurethaneglove fabricated by the invention provides convenience, ease, andsoftness. Even to wear for a long time, there are no allergic reactionsrevealed. The gloves also provide a room temperature surface resistivityof 10⁸˜10 ¹⁰Ω, effectively inhibiting static electricity. Additionally,the powder-free gloves will be applied in electronics and semiconductorindustry. In general glove fabrications, powdered gloves require twelvesteps and 30˜35 min, powder-free chlorinated gloves require 13˜15 stepsand 2˜3 hours, while inner surface polymer-coating composite glovesrequire 12˜15 steps and 1˜2 hours. The present glove fabrication,however, merely requires 6 steps and 30 min, demanding less consumptiontime, occupied space, manpower, and production time. Further, long-termhigh-temperature cross-linking vulcanization is not necessary in theseprocesses, which are benefit for saving power consumption and improvingcompetitive ability of products.

Without intending to limit it in any manner, the invention will befurther illustrated by the following examples.

EXAMPLE 1 Fabrication of PU-A Elastomeric Article

An aqueous aromatic polyurethane dispersion was prepared as follows.10.36 g dimethylol butyric acid (DMBA) and 17.39 g acetone were added toa reaction tank with nitrogen gas, reflux and stirred until a uniformphase was formed. 40.28 g mixture of 2,4-toluene diisocyante and2,6-toluene diisocyanate with a ratio of 80:20 were then added andreacted at 60° C. for 1.5 hours. Next, 119.49 g polytetramethyleneglycol (PTMEG) and 29.87 g polypropylene glycol (PPG) were added andreacted at 60° C. for 4 hours. After cooling to 50° C., 7.07 g triethylamine (TEA) was added to neutralize for 20 min to form neutralized andhydrophilic prepolymers. 190 g such prepolymers were then rapidly addedto 374.3 g deionized water and stirred at 500 rpm to disperse theprepolymers. Till the NCO value lowered to 2.66 wt %, 1.75 g ethylenediamine (EDA) was added to extend the polymer chain at room temperaturefor 2 hours. After acetone was removed by low-vacuum distillation, anaqueous aromatic polyurethane dispersion with 30% solid contents wasprepared.

An aqueous aromatic polyurethane elastomeric article was then fabricatedas follows. A ceramics mold was first dipped in an aqueous solutioncontaining a coagulating agent, and dried at 60° C. to give a pretreatedsurface. Then the mold was dipped in the aqueous aromatic polyurethanedispersion at 30° C. for 30 sec. Next, the mold was slowly lift androtated. An aqueous aromatic polyurethane film with a uniform thicknesswas form on the mold surface. After the further procedure of drying at90° C. for 10 min, cooling and stripping, an aqueous aromaticpolyurethane elastomeric article (PU-A) was formed. The PU-A had anelongation of 700%, a tensile strength of 360 kg/cm², and a 500% modulusof 86 kg/cm².

EXAMPLE 2 Fabrication of PU-B Elastomeric Article

An aqueous aromatic polyurethane dispersion was prepared as follows.10.36 g dimethylol butyric acid (DMBA) and 17.39 g N-methyl pyrrolidone(NMP) were added to a reaction tank with nitrogen gas, reflux andstirred until a uniform phase was formed. 38.05 g mixture of 2,4-toluenediisocyante and 2,6-toluene diisocyanate with a ratio of 80:20 were thenadded and reacted at 60° C. for 1.5 hours. Next, 121.27 gpolytetramethylene glycol (PTMEG) and 30.32 g polypropylene glycol (PPG)were added and reacted at 60° C. for 4 hours. After cooling to 50° C.,7.07 g triethyl amine (TEA) was added to neutralize for 20 min to formneutralized and hydrophilic prepolymers. 190 g such prepolymers werethen rapidly added to 293.7 g deionized water and stirred at 500 rpm todisperse the prepolymers. Till the NCO value lowered to 1.86 wt %, 1.32g ethylene diamine (EDA) was added to extend the polymer chain at roomtemperature for 2 hours. An aqueous aromatic polyurethane dispersionwith 35% solid contents was prepared.

An aqueous aromatic polyurethane elastomeric article was then fabricatedas follows. A ceramics mold was first dipped in an aqueous solutioncontaining a coagulating agent, and dried at 60° C. to give a pretreatedsurface. Then the mold was dipped in the aqueous aromatic polyurethanedispersion at 30° C. for 30 sec. Next, the mold was slowly lift androtated. An aqueous aromatic polyurethane film with a uniform thicknesswas form on the mold surface. After the further procedure of drying at90° C. for 10 min, cooling and stripping, an aqueous aromaticpolyurethane elastomeric article (PU-B) was formed. The PU-B had anelongation of 730%, a tensile strength of 300 kg/cm², and a 500% modulusof 60 kg/cm².

EXAMPLE 3 Fabrication of PU-C Elastomeric Article

An aqueous aromatic polyurethane dispersion was prepared as follows.93.24 g dimethylol butyric acid (DMBA) and 156.52 g N-methyl pyrrolidone(NMP) were added to a reaction tank with nitrogen gas reflux and stirreduntil a uniform phase was formed. 362.51 g mixture of 2,4-toluenediisocyante and 2,6-toluene diisocyanate with a ratio of 80:20 were thenadded and reacted at 60° C. for 1.5 hours. Next, 1034.04 gpolytetramethylene glycol (PTMEG) and 310.21 g polypropylene glycol(PPG) were added and reacted at 60° C. for 4 hours. After cooling to 50°C., 63.63 g triethyl amine (TEA) was added to neutralize for 20 min toform neutralized and hydrophilic prepolymers. 1900 g such prepolymerswere then rapidly added to 2937 g deionized water and stirred at 500 rpmto disperse the prepolymers. Till the NCO value lowered to 2.58 wt %,16.7 g ethylene diamine (EDA) was added to extend the polymer chain atroom temperature for 2 hours. An aqueous aromatic polyurethanedispersion with 35% solid contents was prepared.

An aqueous aromatic polyurethane elastomeric article was then fabricatedas follows. A ceramics mold was first dipped in an aqueous solutioncontaining a coagulating agent, and dried at 60° C. to give a pretreatedsurface. Then the mold was dipped in the aqueous aromatic polyurethanedispersion at 30° C. for 30 sec. Next, the mold was slowly lift androtated. An aqueous aromatic polyurethane film with a uniform thicknesswas form on the mold surface. After the further procedure of drying at90° C. for 10 min, cooling and stripping, an aqueous aromaticpolyurethane elastomeric article (PU-C) was formed. The PU-C had anelongation of 690%, a tensile strength of 400 kg/cm², and a 500% modulusof 28 kg/cm².

Various mechanical characteristics such as elongation, tensile strength,and 500% modulus of PU-A, PU-B, and PU-C elastomeric articles providedby the invention, were compared with that of a related natural rubberlatex glove. The results are illustrated in Table 1. TABLE 1 Tensilestrength 500% modulus Sample Elongation (%) (kg/cm²) (kg/cm²) PU-A 700360 86 PU-B 730 300 60 PU-C 690 400 28 Natural rubber 730 300 60 latexglove

The results indicate that the elastomeric articles of the inventionprovide similar or better mechanical characteristics than conventionalmaterials, such as better elasticity and extensibility (higherelongation and tensile strength) and better donnability, softness, andflexibility (lower 500% modulus).

The elastomeric article fabrication provided by the invention merelyrequires 6 steps and 30 min, demanding less consumption time and processcost. Additionally, long-term high-temperature cross-linkingvulcanization is not necessary in this fabrication, which is benefit forsaving power consumption and improving competitive ability of products.

While the invention has been described by way of examples and in termsof preferred embodiment, it is to be understood that the invention isnot limited thereto. To the contrary, it is intended to cover variousmodifications and similar arrangements (as would be apparent to thoseskilled in the art). Therefore, the scope of the appended claims shouldbe accorded the broadest interpretation so as to encompass all suchmodifications and similar arrangements.

1. An aqueous aromatic polyurethane elastomeric article fabricated by anaqueous aromatic polyurethane dispersion, prepared by polyurethaneprepolymers comprising wholly aromatic diisocyanates.
 2. The aqueousaromatic polyurethane elastomeric article as claimed in claim 1, whereinthe aromatic diisocyanate is toluene diisocyanate (TDI).
 3. The aqueousaromatic polyurethane elastomeric article as claimed in claim 1, whereinthe aqueous aromatic polyurethane dispersion is prepared by an aromaticdiisocyanate, at least one polyol, a low-molecular weight compound withat least two functional groups capable of reacting with isocyanategroups, and a hydrophilic compound containing active hydrogen.
 4. Theaqueous aromatic polyurethane elastomeric article as claimed in claim 1,wherein the elastomeric article has a thickness of 0.05˜0.35 mm.
 5. Theaqueous aromatic polyurethane elastomeric article as claimed in claim 1,wherein the elastomeric article has an elongation of 150˜1000%.
 6. Theaqueous aromatic polyurethane elastomeric article as claimed in claim 1,wherein the elastomeric article has an elongation exceeding 650%.
 7. Theaqueous aromatic polyurethane elastomeric article as claimed in claim 1,wherein the elastomeric article has a tensile strength of 30˜850 kg/cm².8. The aqueous aromatic polyurethane elastomeric article as claimed inclaim 1, wherein the elastomeric article has a tensile strengthexceeding 170 kg/cm².
 9. The aqueous aromatic polyurethane elastomericarticle as claimed in claim 1, wherein the elastomeric article has a500% modulus of 10˜150 kg/cm².
 10. The aqueous aromatic polyurethaneelastomeric article as claimed in claim 1, wherein the elastomericarticle has a 500% modulus less than 70 kg/cm².
 11. The aqueous aromaticpolyurethane elastomeric article as claimed in claim 1, wherein theelastomeric article comprises a glove, condom, or catheter.
 12. A methodof fabricating an aqueous aromatic polyurethane elastomeric article asclaimed in claim 1, comprising: providing an aqueous aromaticpolyurethane solution; dipping a mold in the solution; forming anaqueous aromatic polyurethane film on the mold surface after the mold islift out of the solution; drying and cooling the film; and stripping thefilm and forming an aqueous aromatic polyurethane elastomeric article.13. The method as claimed in claim 12, wherein the aqueous aromaticpolyurethane solution is prepared by the following steps, comprising:mixing aromatic diisocyanate, polyol, hydrophilic groups-containingdiol, and solvent to form a solution comprising aromatic polyurethaneprepolymers; dispersing the prepolymers in an aqueous phase of thesolution and extending the chain thereof; and forming the aqueousaromatic polyurethane solution after the solvent content is reduced bydistillation.
 14. The method as claimed in claim 12, wherein the aqueousaromatic polyurethane solution comprises surfactant, thickener,humectant, stabilizing reagent, deforming agent, cross-linking agent,leveling agent, or plasticizer.
 15. The method as claimed in claim 12,wherein the mold is ceramic, metal, plastic, or rubber.